1. Technical Field
The technical field relates to a car-mounted image recording apparatus and an image recording method capable of imaging the outside scene of a vehicle consecutively and recording efficiently on a recording medium.
2. Related Art
JP-A-2000-6854 discloses a vehicle drive recorder operable to record image information by a CCD camera, and sensor information from a vehicle speed sensor, an acceleration sensor and others in a random access memory while updating sequentially, and transferring the recorded information (image and sensor information) in the random access memory by actuation of an impact sensor when the own vehicle receives an impact, to a nonvolatile flash memory, and recording. As a result, in the event of analysis of an accident, the image and sensor information before the accident recorded in the flash memory can be reproduced, and the situation upon occurrence of the accident can be examined.
JP-A-2007-88541 Patent document 2 discloses an automobile drive recorder operable to record consecutively at a low frame rate usually to suppress the cost of the recording medium, and change the frame rate of recorded image when a magnetic sensor detects a sudden approach of other vehicle. As a result, the accident will be clearly recorded, and the image can be recorded clearly not only in an accident accompanied by a strong impact to cause reaction of the impact sensor, but also in a case of slight contact or near collision not causing reaction of the impact sensor.
JP-A-2005-318519 Patent document 3 discloses a car-mount imaging apparatus in which plural cameras are installed in a vehicle (front left, front right, rear left, rear right, rear, etc.), and when reaching a point registered by the driver, the cameras are changed to the one preset by the driver, and the image taken by this camera is displayed on the monitor. As a result, the image in the direction of high risk of accident determined by the driver is displayed, and the risk of traffic accidents can be lowered.
The vehicle drive recorder of JP-A-2000-6854 records only for several tens of seconds before and after the actuation of the impact sensor. Hence, the situation of a further past time cannot be checked, or the image is not recorded in the event of a small impact not actuating the impact sensor or if the collision is nearly avoided.
The automobile drive recorder of JP-A-2007-88541 records consecutively even if all sensors do not react, and records a clear image by reacting to the magnetic sensor (or human body sensor). However, if the time is too short from reaction of the magnetic sensor (or human body sensor) till collision, the process to the collision may not be recorded clearly, and a collision of an object not reacting to the magnetic sensor (or human body sensor) may not be recorded clearly.
The car-mount imaging apparatus of JP-A-2005-318519 has means for registering a point judged to be important, and displays the image of danger point by changing over to the camera directed in the direction of high risk of accident. However, there is no means for recording the taken image efficiently, and if the taken images are recorded consecutively, a recording medium of large capacity is needed.
Recently, car-mounted image recording apparatuses are used widely for the purpose of preventing crime or recording the scene of a traffic accident. Not limited to taxis and transportation trucks, car-mounted image recording apparatuses are also installed in public transportation means (such as electric trains and city buses). In particular, the car-mounted image recording apparatuses installed in public transportation means are desired to record consecutively during business hours (more than ten hours a day) in order to avoid risk of recording failure. However, recording continuously, the storage capacity in the image recording means of the image recording apparatus becomes enormous. Indeed there is inexpensive image recording means of a large capacity such as hard disk drive (HDD), but the image recording means having a drive device is easily disturbed by vibration, and the recording medium to be mounted on a vehicle is desired to have no drive device. The susceptibility to vibration may be overcome by selecting semiconductor memory or other image recording means not having drive device, but the image recording means having semiconductor memory is very expensive. If the images are recorded consecutively at low image quality throughout the business hours, the storage capacity of the recording medium of the image recording means may be small. But if the image quality is poor in the image recorded at the time of an accident, it is hard to determine the cause of the accident correctly.